The present invention relates to a system for a gearshift of an automobile with an automatic clutch such as an electromagnetic clutch, and more particularly to a system which enables the gearshift to be operated by shifting a shift lever on a straight line.
An electromagnetic powder clutch for an automobile comprises an annular drive member secured to a crankshaft of an engine, a magnetizing coil provided in the drive member, a driven member secured to an input shaft of a transmission spaced so as to leave a gap from the drive member, and a shift lever for changing gears in the transmission. The shift lever is provided with a tilted knob and switches. The knob is tiled with respect to the shift lever by a force applied through the driver's hand, when the shift lever is shifted. The switches are actuated by the knob for controlling the electric current flowing in the magnetizing coil. As an accelerator pedal is depressed, the clutch current passing through the coil increases. The magnetic powder is aggregated in the gap between the drive member and the driven member, so that the driven member is coupled to the drive member. Thus, the automobile can be smoothly started by suitably depressing the accelerator pedal with slippage of the clutch. Such a system is disclosed in a plurality of patent publications, for example, in Japanese patent laid-open specification No. 56-60733.
Today, many cars are equipped with four-speed transmissions. Accordingly, the shift lever must be shifted along an H-shaped shift pattern for the forward driving. Although no clutch pedal operation is required in such a car, the driver is not yet free from a complex shift lever operation.
In order to simplify the operation of the shift lever, I have disclosed a gearshift system in my co-pending patent application Ser. No. 524,948 filed on Aug. 22, 1983, the same date as the filing of the present patent application, in which four forward-gear sets of a transmission are shifted by shifting a shift lever on a straight line. In the system, the four forward-gear sets are divided into a high power transmission system and a low power transmission system, and an electric actuator is provided for operating a select device to select one of the power systems. The low power transmission is designed to produce sufficient power to start and drive an automobile on flat roads. However, the electromagnetic clutch control system is so arranged as to cause the electromagnetic clutch to slip for a long time at the engagement thereof during the low power transmission driving. Therefore, if the automobile is driven only by the low power transmission, the clutch tends to overheat causing damage to engaging member and electric conductors.